Ohmic Contact to p-Type GaN Enabled by Post-Growth Diffusion of Magnesium

We demonstrated the formation of excellent Ohmic contact to <tex-math notation="LaTeX">p </tex-math> -type GaN (including the plasma etching-damaged <tex-math notation="LaTeX">p </tex-math> -type GaN which otherwise exhibited undetectable current within ±5 V) by the post-growth diffusion of magnesium. The specific contact resistivity on the order of <tex-math notation="LaTeX">10^-4\,\,Ω </tex-math> .cm 2 (extracted at V = 0 V) was achieved on the plasma-damaged <tex-math notation="LaTeX">p </tex-math> -GaN with linear current-voltage characteristics by the transfer length method (TLM) measurement. The improvement in current by a factor of over 10 9 was also obtained on the plasma-damaged p-n junction diode after the same Mg-treatment. These experimental results indicate a great potential of post-growth diffusion of Mg to overcome the bottleneck of forming a good Ohmic contact to <tex-math notation="LaTeX">p </tex-math> -GaN.